Alternating-current motor.



M. C. A. LATOUR.

ALTERNATING CURRENT MOTOR.

Armcmou FILED ocr. 2a. 1914.

1,192,649. Patented July 25, 1916.

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M. C. A. LATOUR.

ALTERNATING CURRENT MOTOR.

APPLICATION FILED OCT. 28, I914.

Patented July 25, 1916.

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UNITED STATES PATENT OFFICE.

MARIUS C. A. LATOUR, OF PARIS, FRANCE, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

ALTERNATING-CURRENT MOTOR.

Specification of Letters Patent.

Patented July 25, 1916.

T 0 all whom it may concern:

Be it known that I, MARIUS O. A. LA'roUR, a citizen of the Republic ofFrance, residing at Paris, France, have invented certain new and usefulimprovements in Alternating-Current Motors, of which the following is aspecification.

My invention relates to alternating current motors, and moreparticularly to alternating current compensated series motors.

The object of my invention is generally to improve the commutation of analternating current compensated series motor, and particularly toprovide a novel and improved arrangement for a motor of this typewhereby it is enabled to operate substantially sparklessly.

I have heretofore suggested, as hereinafter mentioned, as a means forimproving the commutation of a compensated series motor for alternatingcurrent, a closed circuit connection about the motor-armature includingan auxiliary electromotive force of the proper phase for producing acurrent for producing a commutating field, and I have further suggesteda means for obtaining this auxiliary electromotive force from theelectromotive force of the main source of energy supply modified by anelectromotive force derived from a transformer connected in series withthe motor.

More specifically, the object of my present invention is then to providean improved and satisfactory means for obtaining an electromotiveforceof the proper phase for connection in a local circuit about themotorarmature for producing a current for producing a commutating field,and particularly such an electromotive force having one componentdependent in phase upon the voltage impressed on the motor and a secondcomponent dependent in phaseupon the motor current.

The novel features of my present invention which I believe to bepatentable are definitely indicated in the claim appended hereto.

The nature of my invention and its ap plication to alternating currentcompensated series motors will be understood from the followingdescription taken in connection with the accompanying drawings, inwhich:

Figure 1 is a diagrammatic view of my invention applied to a singlephase alternating current compensated series motor; Fig. 2 is a modifiedform of the application of my invention to such a motor; Fig. 3 is astill further modification of the invention; and Fig. 4 is adiagrammatic view of my invention applied to a plurality of compensatedseries motors connected in series with each other.

In French Patent No. 355,687, granted to me September 8th, 1905, and inUnited States Patent No. 841,257, granted to me June 15th, 1907, I havedisclosed in combination with a compensated series motor for alternatingcurrent means for connecting the motorarmature in a closed circuit witha source of electromotive force of proper phase for producing a currentfor producing a commutating field. As described in these patents, thesource of electromotive force employed has one component dependent inphase upon the voltage impressed on the motor and a second componentdependent in phase on the motor current. As illustrated in Fig. 5 of theFrench patent and in Fig. 3 of the United States patent, anelectromotive force of the proper phase for connection across themotor-armature to produce the necessary commutating field may beobtained by an electromotive force derived from the main source ofenergy supply modified by an electromotive force derived from thesecondary winding of a transformer connected in series with the motor.The electromotive force component derived from the main source of supplyis in phase with the voltage impressed on the motor, while theelectromotive force component derived from the secondary winding of theseries transformer is substantially ninety degrees out of phase with thecurrent in the primary winding and varies with variations in themagnitude of the primary current. The primary andsecondary windings ofthe series transformer are thus traversed by currents in quadrature withrespect to time phase. It follows therefrom that the resultant of theprimary and secondary ampere turns of the series transformer may berelatively large, that is to say, even of the order of magniture of theprimary or secondary ampere turns. Inasmuch as it is the resultant ofthe primary and secondary ampere turns which must be taken into accountin the design of the magnetic circuit of the transformer, it will beevident that, unless certain precautionary provisions are taken, only a.very small number of turns should be arranged on the transfin-mer. Thenormal number of turns for the primary and secondary windings of thetransformer would produce excessive saturation of the transformer, whichwould upset normal working conditions. That is to say, the normal numberof primary and secondary ampere turns would cause the magnetic circuitof a transformer of ordinary size to become saturated, and in order toprevent saturation, the magnetic material of the tltll'lSfOl'lllQl'would have to be very roluminous, and hence the cost of the transformerwould be excessive. @n the other hand, if the transformer is providedwith a small number of primary and secondary turns there is a very badutilization of the magnetic circuit.

In aceordan e with my present invention, the series transformer isprovided with an air gap in its magnetic circuit, under which conditionthe resultant of the primary and secondary ampere turns, even if theprimary and secondary windings of the transformer have the normal numberof turns, will not give rise to any disturbing phenomena in thesaturation. This application of my invention results in providing atransformer reduced both in volume or size, or in cost.

My invention will be better understood by reference to the accompanyingdrawings, which diagrammatically illustrate the in ycntion applied invarious ways to compensated se 'ies motors for alternating current.

In each of the figures of the accompanying drawings, I have representeda single phase compensated series motor connected to the secondarywinding of a main transformer 10. The compensated series motor isparticularly adapted for railway work, and I hare, accordingly,represented the primary of the trai'isformer 10 connected be tween atrolley wire and ground. The compensated series motor comprises a.(fOl11])tIl sating winding 11, an exciting or field winding 12. and anarmature 11-; carrying a commutated armature winding. Brushes 14c bearon the commutator connected to the ar mature winding in the usualmanner, and the compensating, field and armature windings are connectedin series, as is well un derstood. The field winding 12 produces anexciting field at right angles to that pro duced by the armaturecurrent, andthe c empensating winding 11 produces a field in line withthe axis of the armature reaction, so as to neutralize the armaturereaction in the manner well understood in the art.

.ln accordane with my prior patents the primary winding 15 of atransformer is connected in series with the motor, and the secondarywinding 16 of this transformer is connected in a local circuit includingthe motor-armature and a section of the secondary winding of the maintransformer ll). This local circuit also contains an adjust ableresistance 17. It commutating field electromotive force, having onecomponent in phase with the voltage impressed on the motor and a secondcomponent depemlent in phase upon the current flowing through the motor,is thus impressed on the commutator brusl'ies. By varying the twocomponents of the electromotive force in the closed circuit about them:1tor-armature, the motor may be adjusted for substantially sparklesscommutation over widely varying speeds.

In accordance with my present invention, the magnetic circuit of theseries transformer has an air-gap, preferably adjustable, so that betterconditions of commutation may be obtained at different speeds. In thefigures of the accon'ipanying drawings, I have, for the purpose ofillustration, represented the magnetic circuit of the transformercomposed of two independent members, the first a main U-shapcd member20, upon which the primary and secondary windings are mounted, and thesecond a movable magnetic armature or keeper 21 adapted to complete themagnetic circuit from one leg of the U-shaped member to the other. Theair-gap between the U- shaped member 20 and the keeper 2i nniy beadjusted by turning a screwdiandle 2 as will be readily understood froman inspection of the drawings. It will be evidei "i from the foregoingexplanation that the provision of an air-gap in the magnetic circuit ofthe series transformer permits the use of a normal number of primary andsecondary turns without necessitating an excessive amount of magneticmaterial in the magnetic circuit of the transformer, in o1.'- der toprevent saturation, due to the large magnitude of the resultant of theprim: ry and secondary ampere turns.

In each of the examples of my invention illustrated in the figures ofthe accompairving drawings, the value of both components of theelectromotive force included in the closed circuit about the motor-a iaturemay be adjusted to secure the proper phase and magnitude of theresultant electromotive force to produce a connnutating lield of theproper phase and amount for enabling the motor to operate sparklessly atany given speed within limits. Thus the component of this electromotiveforce in phase with the yoltage impressed on the motor may be adjustedby means of the adjustable connection of the conductor 2st to thesecondary winding of the main transformer 10, and the componentdependent in. phase upon the motor current may be adjusted by means ofthe adjustable connection of the conductor 25 to the secondary winding16 of the series transformer.

The variable ratio of transformation of the series tranformer serves toinsure perfect connnutation at varying speeds of the motor. Thetransformation-ratio may be governed or varied in accordance with theelectromotive force placed in opposition on the armature of the motor bythe main feed transformer. This variation of the transformation-ratiomay be accomplished automatically as a function of the speed of themotor, for example by means of a centrifugal speed governor. Thismodification of my invention is illustrated in Fig. 2 of the drawings. Aspeed. responsive device, such as a centrifugal speed governor 2G,operativclv connected to the rotatable shaft of the motor, automaticallymanipulates an adjustable contact 27 to vary the number of turns of thesecondary winding of the series transformer included in the closedcircuit about the motor-armature as a function of the speed of themotor. It will also be noted that in Fig. 2 of the drawings the primarywinding 15 of the series transformer is connected between thecompensating winding 11 of the stator of the motor and the armature 13,instead of between the armature and the main transformer, as in Fig. 1of the drawings. The insulation between the primary and secondarywindings of the series transformer may be heavy when the primary windingis connected as illustrated in Fig. 2.

In Fig. 3 of the drawings 1 have illustrated a further modification ofmy invention, in that a connection is employed for operating the motoras a repulsion motor. \Vhen the motor is starting, the switch contacts30 are bridged by a movable metallic bar 31 and a local short-circuit isprovided about the motor armature. The motor thus starts as a repulsionmotor. Vhen a predetermined speed is attained, a speed responsivedevice, such as the centrifugal governor operatively connected to therotor of the motor and to the bar 31, lifts the bar 31, and the contacts33 are thereby bridged. The contacts 33 remain closed by the bar 31 aslong as the speed of the motor remains above such predetermined speed,and in this condition the motor connections are the same as representedin the motor of Fig. 1 of the drawings. The motor illustrated in Fig. 3of the drawings thus starts as a repulsion motor without the applicationof the invention of my prior patents, but runs normally, that is whenthe speed exceeds a predetermined value, with a connection utilizingsuch invention.

here a plurality of motors are in use, a

single series transformer may be employed for all. Assuming the case oftwo motors and referring to Fig. 1 of the drawings, it will. be seenthat two compensated series motors are connected in series with eachother and that my invention is applied to these motors through a singletransformer connected in series relation with the two motors. Startingwith the adjustable connection to the secondary winding of the maintransformer 10, the electric circuit is through the two compensatingwindings 11 and 11 arranged in series relation to one another, thencethrough the two field windings 12 and 12 similarly related in series,then through the armature windings of the two armatures 13 and 13, andfinally through the primary winding 15 of the series transformer to theother terminal of the main transformer. The two armatures 13 and 13connected in series are closed through a single local circuit includingthe secondary winding 16 of the series transformer, the adjustableresistance 17 and an adjustable portion of the secondary winding of themain transformer 10. It will be seen that the corresponding parts of thetwo motors are separately connected in series, the order of theseries-connected compensating windings, on the one hand, and the seriesconnected field windings, on the other hand, being, however, immaterial.

WVhile I have herein specifically shown and described the seriestransformer as having two separate windings, it will be obvious to thoseskilled in the art that a single winding may serve the function of both;in other words, that a compensator connected in series relation with themotor may be employed, if desired, in place of the series transformer.

It will, of course, be understood that my invention is not limited tothe specific modifications herein illustrated. Thus, While I haveexplained my invention by illustrating and describing certainembodiments thereof, it will be understood that the invention may beembodied in other forms than that shown and described. I, accordingly,do not wish to be restricted to the particular forms and constructionsdiagrammatically represented herein by way of example for the purpose ofsetting forth my invention in accordance with the patent statutes. Theterms of the appended claim are, therefore, not restricted to theprecise structures disclosed, but are intended to cover all changes andmodifications within the spirit and scope of my invention.

WVhat I claim as new and desire to secure by Letters Patent of theUnited States, is

The combination with an alternating current motor having a compensatingwinding an exciting winding and an armature winding conductivelyconnected in series, and a 4 1,192,6&9

transformer having its primary winding i11- iliary electrolnotive forcedependent in phase eluded 1n the serles en'cult o1": sa1d three n10-npon the voltage nnpressed on the motor. tor \Ylndlngs and havlng an angap 111 us I have hereunto set my hand thls 12th day magnetle ell-cult,01 aloeal en'enlt lnelndlng of October, 191%. 4 saic armature \vindinanl th s eondu' Y r r 1 a C 6 e L 9 MARIUS e. A. LATOUR. \undlng of sandtransfonner and an aun- Copies 421 this patent may be obtained for fivecents each, by addressing the Commissioner of Patents.

Washington, D. C.

